This application is based upon application No. 2002-349843 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to a lens barrel, and particularly relates to the lens barrel which is suitable for a multistage zoom lens (or multiple-step zoom lens).
2. Description of the Related Art
Conventionally, there have been proposed a variety of lens barrels each of which is of a type in which the lens barrel can be projected from its camera body. For examples, each of Japanese Laid-Open Patent Publication No. 2000-66081 and Japanese Laid-Open Patent Publication No. 2001-183563 discloses a lens barrel which is of the type in which the lens barrel can be projected from its camera body by two steps or by two stages. On the other hand, U.S. Pat. No. 6,052,535 discloses a lens barrel which is of the type in which the lens barrel can be projected from its camera body by three steps or by three stages.
The conventional zoom lens barrel which projects from its camera body by two steps, generally, has a straight-moving member which is guided linearly by a fixed barrel (or a stationary barrel), and it has a first rotation member which is positioned radially outside the straight-moving member, which moves integrally therewith in a direction of its optical axis, and which is rotatable relative to the straight-moving member. In addition, the zoom lens barrel has a second rotation member which is positioned radially inside the straight-moving member, which moves relative to the straight-moving member in the direction of the optical axis, and which rotates and interlocks with the first rotation member, where a rotation interlocking piece mounted on the second rotation member is inserted inside an elongate hole formed on the straight-moving member.
According to the conventional zoom lens barrel, however, many components or elements superimpose one over another in its radial direction. Therefore, it is difficult to make the zoom lens barrel small or compact. Also, because the straight-moving member has a low rigidity owing to the presence of the elongate hole, it is difficult to realize a high accuracy for driving and a high anti-shock nature (or a high shock-resistant nature). Also, because there is need of adding a light blocking member (or a light shielding member) in the mechanism, it is difficult to avoid a high cost thereof. Also, in a case of developing the mechanism of the projection of the zoom lens barrel by two steps into a mechanism of the projection of the zoom lens barrel by three steps, there arises a problem of how the straight-moving interlocking mechanism for limiting its rotation should be constructed.
Also, the multistage projection tripe of lens barrel has a straight-moving member for limiting the rotation thereof, and it has a rotation member which rotates relative to the straight-moving member. More specifically, in the mechanism, there are provided a plurality of pairs, each of which is composed of the straight-moving member and the rotation member, and each of which moves integrally in the direction of the optical axis. Between the adjacent pairs, the straight-moving members are interlocked with each other in terms of their straight movement, and the rotation members are interlocked with each other in terms of their rotation. The pairs move relative to each other in the direction of the optical axis on the basis of mutual engagement between the straight-moving member of one of the adjacent pairs and the straight-moving member of the other thereof, so that the lens barrel can project (or expand) and contract (or retract).
The conventional lens barrel having the mechanism of projection by more than two steps, has a construction in which there is mounted the straight-moving member between the front and rear rotation members.
For example, in a case of a mechanism in which the rotation member of one of the pairs is connected to the straight-moving member of the other of the pairs by screw so that the one of the pairs projects from the other of the pairs in which the rotation member is arranged radialy and outwardly of the straight-moving member, there is need of forming a space extending spirally (or helically) on the straight-moving member of the other of the pairs in order to transmit rotation between the rotation member of the one of the pairs and the rotation member of the other thereof.
According to the mechanism, the rigidity of the straight-moving member of the other of the pairs is relatively lower owing to the spiral space formed therein. Therefore, for example, considering the exertion of any excessive power on the lens barrel in the axial direction, not only there exists a limitation to reduction of dimension of the straight-moving member of the other of the pairs in the radial direction, but also there exists a limitation to increase, for increasing the accuracy in control, of rotational angle of the rotation member. Furthermore, in order to prevent light from entering the spiral space of the straight-moving member of the other of the pairs, the light blocking mechanism (or light shielding mechanism) can not help but be complicated in structure.
Accordingly, there has not yet been provided a lens barrel, with a low cost and a high rigidity thereof, having a mechanism of projection thereof by more than two steps, in which the lens barrel is compact or small-sized.
Therefore, it is an object of the present invention to provide a lens barrel which can project and retract by taking more than two steps or stages, in which the lens barrel can be downsized or can be made compact.
In accomplishing this and other objects of the present invention, according to one aspect thereof, there is provided a lens barrel comprising: a fixed lens barrel member; a first straight-moving member for guiding a first lens barrel member movably in an axial direction of the fixed lens barrel member; a second straight-moving member for guiding a second lens barrel member movably in the axial direction of the fixed lens barrel member, in which the second straight-moving member is provided generally on a same circle or circumference, in a plane perpendicular to the axial direction thereof, as that of the first straight-moving member; and a third straight-moving member for guiding a third lens barrel member movably in the axial direction of the fixed lens barrel member, in which the third straight-moving member is provided generally on the same circle or circumference, in the plane perpendicular to the axial direction thereof, as that of the first straight-moving member.
In the mechanism, a first pair composed of the first straight-moving member and the first lens barrel member as a first step (or as a first stage, or as a first level) with respect to the fixed lens barrel member, a second pair composed of the second straight-moving member and the second lens barrel member as a second step (or as a second stage, or as a second level) therewith, and a third pair composed of the third straight-moving member and the third lens barrel member as a third step (or as a third stage, or as a third level) therewith, can project from each other with respect to the fixed lens barrel. According to the mechanism, the first straight-moving member, the second straight-moving member and the third straight-moving member, are provided or arranged generally on the same circumference, or circle, in the plane perpendicular to the axial direction of the fixed lens barrel. Consequently, with the mechanism, the thickness of the first straight-moving member, the thickness of the second straight-moving member and the thickness of the third straight-moving member, do not accumulate in a direction of radius of the lens barrel; therefore, the lens barrel which can project and retract by taking more than two steps and which can be made compact in size, is provided.
As an embodiment, a lens barrel member of at least one of the first pair, the second pair, and the third pair, is relatively rotatably connected to its corresponding straight-moving member, in which the lens barrel member and the straight-moving member can move integrally in the axial direction.
As an embodiment, a location of each of the first straight-moving member, the second straight-moving member and the third straight-moving member, is more inward radially than any location of the first lens barrel member, the second lens barrel member and the third lens barrel member.
In accomplishing the above objects of the present invention, according to another aspect thereof, there is provided a lens barrel comprising: a fixed member; a first pair which has a first straight-moving member having a straight-moving interlocking part wherein the first straight-moving member is movably guided by the fixed member in an axial direction of the lens barrel, and which has a first rotation member that is relatively rotatably connected to the first straight-moving member, wherein the first rotation member moves integrally with the first straight-moving member in the axial direction; a second pair which has a second straight-moving member having a first straight-moving interlocking part that engages movably with the straight-moving interlocking part of the first straight-moving member in the axial direction and having a second straight-moving interlocking part different from the first straight-moving interlocking part, and which has a second rotation member that is relatively rotatably connected to the second straight-moving member, wherein the second rotation member moves integrally with the second straight-moving member in the axial direction, and wherein the second pair can project on a side of an object to be photographed with respect to the first pair; and a third pair which has a third straight-moving member having a straight-moving interlocking part that engages movably with the second straight-moving interlocking part of the second straight-moving member in the axial direction, and which has a third rotation member that is relatively rotatably connected to the third straight-moving member, wherein the third rotation member moves integrally with the third straight-moving member in the axial direction, and wherein the third pair can project on the side of the object to be photographed with respect to the second pair, wherein the straight-moving interlocking part of the first straight-moving member, the first straight-moving interlocking part of the second straight-moving member, the second straight-moving interlocking part of the second straight-moving member, and the straight-moving interlocking part of the third straight-moving member, are provided or arranged generally on a same circle or circumference in a plane perpendicular to the axial direction thereof.
In other words, the zoom lens barrel includes at least three pairs, each of which has a straight-moving member (i.e. first straight-moving member, second straight-moving member or third straight-moving member) that is prevented from rotating, and each of which has a rotation member (i.e. first rotation member, second rotation member or third rotation member) that is rotatably connected to the straight-moving member and that moves integrally together with the straight-moving member in the axial direction of the lens barrel. In the mechanism, the straight-moving interlocking parts of the three pairs engage with each other movably in the axial direction, and each of the straight-moving interlocking members of the three pairs is arranged generally on the same circle or circumference in the plane perpendicular to the axial direction.
In the mechanism, the mutual engagement between the straight-moving interlocking parts of the three straight-moving members prevents mutual rotation between the straight-moving members. In the mechanism, the straight-moving member and/or the rotation member, in each pair, can have a cam (or cams), a helicoid (or helicoids), or the like, by which the pairs can move relative to each other and relative to the fixed member in the axial direction due to the rotation of the rotation members relative to the straight-moving members, so that at least the three pairs (i.e. first pair, second pair and third pair) can project, as at least three steps, from the fixed member.
According to the mechanism, when the rotation member rotates relative to the straight-moving member, a force for stopping, or blocking, the rotation of the rotation member, is exerted on a circumference, or periphery, of the straight-moving member. Although the force therefore is exerted on, or transmitted to, each of the straight-moving interlocking parts of the first, second and third straight-moving members, the path for transmitting the force does not deviate in the radial direction of the lens barrel because each of the straight-moving interlocking parts thereof are provided generally on the same circumference, or circle, in the plane perpendicular to the axial direction. In other words, the location, or position, of action of force exerting thereon in the circumferential direction, does not deviate radially between the straight-moving interlocking parts thereof back and forth in the axial direction, and thus any couple of forces due to such a deviation in the location of action of force do no occur. Therefore, with the mechanism, it is possible to assure enough strength of the straight-moving members without making the straight-moving members bigger or larger in size.
Consequently, with the mechanism, the lens barrel which can project and retract by taking more than two steps, in which the lens barrel can be downsized or can be made compact, is provided.
As an embodiment, each of the straight-moving interlocking part of the first straight-moving member, the first straight-moving interlocking part of the second straight-moving member, the second straight-moving interlocking part of the second straight-moving member, and the straight-moving interlocking part of the third straight-moving member, is more inward radially than any location of the first rotation member, the second rotation member and the third rotation member.
According to the mechanism, each of the rotation members locates more outwardly in terms of the radial direction than each of the straight-moving interlocking parts; in other words, each of the former is arranged outside each of the latter. Therefore, it is possible to prevent the rotation interlocking mechanism for rotatably interlocking the rotation members with each other from interfering with the straight-moving member. Hence, with the mechanism, there is no need of providing a hole, or the like, on the straight-moving member for avoiding any interference with the rotation interlocking mechanism. In the mechanism, for example, the rotation member of one of adjacent pairs can be connected to the straight-moving member of the other of the adjacent pairs by a helicoid so that the lens barrel can project (or expand) and retract (or contract).
Accordingly, with the mechanism, the rigidity of the lens barrel is enhanced.
As an embodiment, the second straight-moving member of the second pair has more than one arm which adjoin the straight-moving interlocking part of the third straight-moving member, in which the more than one arm locate on the same circle in the plane perpendicular to the axial direction, and in which the more than one arm form the second straight-moving interlocking part of the second straight-moving member, and wherein at least one of the more than one arm has an insertion opening which is formed by cutting a body thereof from a side opposite to an object to be photographed in the axial direction, with a state in which the insertion opening is closed by a part of the body on a side of the object, and wherein the straight-moving interlocking part of the first straight-moving member is inserted into the insertion opening.
According to the mechanism, the insertion opening does not exist on a part of the body of the arm on the side of the object to be photographed; in other words, both edges of the body on the side of the object, defining the insertion opening, in the peripheral direction of the second straight-moving interlocking part, are connected to each other by the part of the body of the arm. Therefore, with the mechanism, the reduction in rigidity of the arm is effectively prevented, and accuracy of the lens barrel is secured and maintained.
As an embodiment, the first straight-moving member of the first pair has at least one arm which is adjacent to the first straight-moving interlocking part of the second straight-moving member, in which the arm is on the same circle in a plane perpendicular to the axial direction thereof, and in which the straight-moving interlocking part is formed on the at least one arm, wherein the at least one arm is arranged in a direction which is generally same as a direction in which a pair of longer sides of a rectangular light-receiving surface for receiving light focussed by the lens barrel oppose each other.
Regarding position of the arm of the first straight-moving member, in a case where the arm is mounted inwardly radially, there is a possibility that the arm may interfere with the flux of light (or beam of light) on the light receiving surface. On the other hand, however, interference of the arm with the flux of light reaching outside the light receiving surface, does not bring any problem. Considering these situations, it is advantageous to arrange the arm(s) in the direction which is generally same as the direction in which the pair of longer sides of the rectangular light-receiving surface face each other in a case that the light-receiving surface is rectangular in shape, because the area for allowing the arm to be arranged without such an interference is larger on the longer sides of the rectangular light-receiving surface than the shorter sides thereof. Accordingly, with the arrangement, not only the interference of the flux of light with the arm relative to the light-receiving surface is effectively prevented, but also the arm can be positioned more inwards radially, thus possible to make the lens barrel more compact. In the arrangement, it is preferable to mount a pair of the arms thereon, from a view point of strength and balance of the lens barrel.
In the mechanism, for example, the second straight-moving member of the second pair can have three arms which adjoin the straight-moving interlocking part of the third straight-moving member, in which the three arms locate on the same circumference in the plane perpendicular to the axial direction, and in which the three arms form the second straight-moving interlocking part of the second straight-moving member. Each of two of the three arms has an insertion opening, or space, through which the straight-moving interlocking part of the first straight-moving member is inserted, and the two of the three arms form the first straight-moving interlocking part of the second straight-moving member.
As an embodiment, at least one lens frame is mounted more inward than any one of the straight-moving interlocking part of the first straight-moving member, the first straight-moving interlocking part of the second straight-moving member, the second straight-moving interlocking part thereof, and the straight-moving interlocking part of the third straight-moving member, wherein the lens frame has an engagement part which projects radially outwardly, in which the engagement part engages with at least one rotation member which is selected from the first rotation member, the second rotation member and the third rotation member, and engage with at least one straight-moving member which is selected from the first straight-moving member, the second straight-moving member and the third straight-moving member, in which the at least one rotation member and the at least one straight-moving member form at least one pair which is selected from the first pair, the second pair and the third pair.
According to the mechanism, when the rotation member rotates relative to the corresponding straight-moving member in the pair, the at least one lens frame is moved relative to the pair in the axial direction. The engagement part, for example, can include a straight-moving guiding part which is guided linearly by the straight-moving interlocking part of the straight-moving member, and can include a cam follower which is guided by a spiral cam groove, or a spiral cam projection streak, provided on the corresponding rotation member.
According to the mechanism, the projection (or expansion) and the retraction (or contraction) of the lens barrel, and the movement of the lens, are performed with the same member, it is possible to make the lens barrel small-sized (or compact) and to realize a low cost thereof.
The engagement part of the lens frame is not necessarily required to engage with the rotation member and the straight-moving member of a particular pair. Alternatively, the engagement part thereof can be switched over between a first state in which the engagement part thereof engages with the rotation member and the straight-moving member of the particular pair, and a second state in which the engagement part thereof engages with the rotation member and the straight-moving member of another pair.
As an embodiment, a rotation member of one of the first pair and the second pair engages generally spirally with a straight-moving member of the other of the first pair and the second pair, in which the rotation member is one of the first rotation member and the second rotation member, and in which the straight-moving member is one of the second straight-moving member and the first straight-moving member.
As an embodiment, a rotation member of one of the second pair and the third pair engages generally spirally with a straight-moving member of the other of the second pair and the third pair, in which the rotation member is one of the second rotation member and the third rotation member, and in which the straight-moving member is one of the third straight-moving member and the second straight-moving member.
As an embodiment, a spirally engaging part of each of the rotation member and the corresponding straight-moving member extends continuously in a direction of its circumference, respectively.
In accomplishing the above objects of the present invention, according to still another aspect thereof, there is provided a lens barrel comprising: a fixed member; a first pair which has a first straight-moving member that movably engages with the fixed member in an axial direction of the lens barrel in which the first straight-moving member is guided linearly by the fixed member, and which has a first rotation member that is relatively rotatably connected to the first straight-moving member in which the first rotation member integrally moves together with the first straight-moving member in the axial direction thereof, wherein the first pair can project towards an object to be photographed with respect to the fixed member; a second pair which has a second straight-moving member that movably engages with the first straight-moving member in the axial direction, in which the second straight-moving member is guided linearly, and which has a second rotation member that is relatively rotatably connected to the second straight-moving member, in which the second rotation member integrally moves together with the second straight-moving member in the axial direction thereof, in which the second rotation member movably engages with the first rotation member in the axial direction with a state in which the second rotation member is prevented from rotating relative to the first rotation member, wherein the second pair can project towards the object to be photographed with respect to the first pair; and a third pair which has a third straight-moving member that movably engages with the second straight-moving member in the axial direction, in which the third straight-moving member is guided linearly, and which has a third rotation member that is relatively rotatably connected to the third straight-moving member, in which the third rotation member integrally moves together with the third straight-moving member in the axial direction thereof, in which the third rotation member movably engages with the second rotation member in the axial direction with a state in which the third rotation member is prevented from rotating relative to the second rotation member, wherein the third pair can project towards the object to be photographed with respect to the second pair, wherein a part of the second straight-moving member and a part of the first straight-moving member which movably engage with each other in the axial direction, are provided more inwardly radially than any one of the first rotation member and the second rotation member, wherein a part of the third straight-moving member and the part of the second straight-moving member which movably engage with each other in the axial direction, are provided more inwardly radially than any one of the second rotation member and the third rotation member, wherein the fixed member and the first rotation member are connected to each other by a drive force transmission mechanism for transforming a rotation drive force into a straight-moving drive force and for transmitting the straight-moving drive force, wherein the first rotation member and the second straight-moving member are connected to each other by a drive force transmission mechanism for transforming the rotation drive force into a straight-moving drive force and for transmitting the straight-moving drive force, and wherein the second rotation member and the third straight-moving member are connected to each other by a drive force transmission mechanism for transforming the rotation drive force into a straight-moving drive force and for transmitting the straight-moving drive force.
According to the mechanism, the first pair, the second pair, and the third pair, can project from the fixed member by three steps (or by three stages). In the mechanism, the drive force transmission mechanism can comprise a screw-connecting mechanism (or a helicoid-connecting mechanism), a cam-connecting mechanism, or the like.
In the mechanism, the first straight-moving member dose not intervene between the first rotation member and the second rotation member; and the second straight-moving member dose not intervene between the second rotation member and the third rotation member. With the mechanism, rotation, or rotation force, can be transmitted between the rotation members, and there is no need of making or forming a spiral space, or opening, on the straight-moving member.
According to the mechanism, there is no need of employing a component, or an element, having such a spiral space or opening which may incur reduction in rigidity thereof; therefore, it is possible to make a component or an element therefor smaller. In addition, with the mechanism, it is possible to enhance an accuracy of control by increasing the rotation angle of the rotation member. Also, with the mechanism, it is possible to realize a shielding of light by a simple construction. Also, according to the mechanism, there is no straight-moving member between the rotation members; therefore, it is possible to simplify the construction, or mechanism, for transmitting the rotation, or rotational force, between the rotation members.
Therefore, with the mechanism, the lens barrel can be downsized, or can be made compact or small.
Furthermore, in a case that a screw-connecting mechanism is employed for the drive force transmission mechanism for projecting and retracting the lens barrel, the part or region which the force is transmitted to, or exerted upon, is arranged around the periphery or circumference of the lens barrel. Therefore, with the mechanism, the rigidity of the lens barrel is surely enhanced.
As an embodiment, the first rotation member and the second straight-moving member are connected to each other by a screw which extends all around each of the first rotation member and the second straight-moving member, and wherein the second rotation member and the third straight-moving member are connected to each other by a screw which extends all around each of the second rotation member and the third straight-moving member.
According to the mechanism, the screw connecting mechanism exists all around each of the first rotation member, the second straight-moving member, the second rotation member, and the third straight-moving member. Therefore, with such a simple mechanism, the connecting part between the members is shielded all around them from light.
As an embodiment, the first straight-moving member has a first straight-moving interlocking part which extends in the axial direction, wherein the first rotation member has a helicoid on an inner surface thereof and has a rotation interlocking groove on the inner surface thereof, in which the rotation interlocking groove extends in the axial direction, and in which the rotation interlocking groove is formed by cutting out the helicoid radially up to a predetermined depth thereof, wherein the second straight-moving member has a second straight-moving interlocking part which extends in the axial direction, in which the second straight-moving interlocking part movably engages with the first straight-moving interlocking part in the axial direction, wherein the second rotation member has a projection on an outer surface thereof, in which the projection engages with the rotation interlocking groove of the first rotation member, in which the second rotation member has a helicoid on an inner surface thereof and has a rotation interlocking groove on the inner surface thereof, in which the rotation interlocking groove extends in the axial direction, and in which the rotation interlocking groove is formed by cutting out the helicoid radially up to a predetermined depth thereof, wherein the third straight-moving member has a third straight-moving interlocking part which extends in the axial direction, in which the third straight-moving interlocking part movably engages with the second straight-moving interlocking part in the axial direction, wherein the third rotation member has a projection on an outer surface thereof, in which the projection engages with the rotation interlocking groove of the second rotation member, wherein the first straight-moving interlocking part is arranged more inward radially than any one of the first rotation member and the second rotation member, and wherein the second straight-moving interlocking part is arranged more inward radially than any one of the second rotation member and the third rotation member.
According to the mechanism, the rotation interlocking groove in each of the first rotation member and the second rotation member is formed by cutting out the inner helicoid radially up to a predetermined depth thereof; namely, the rotation interlocking groove is formed by cutting the inner helicoid from inside towards outside up to the predetermined depth radially. Therefore, even if such a rotation interlocking groove is provided on each of the first rotation member and the second rotation member, light is prevented from entering therebetween by the helicoid connection parts.
As an embodiment, each of the first straight-moving interlocking part, the second straight-moving interlocking part and the third straight-moving interlocking part, is provided generally on the same circle or circumference which locates radially inside any one of the first rotation member, the second rotation member and the third rotation member.
According to the mechanism, each of radial thickness of the first straight-moving interlocking part, the second straight-moving interlocking part and the third straight-moving interlocking part, does not accumulate one over another. Therefore, with the mechanism, it is possible to make the lens barrel small and compact in size in the radial direction.